The present invention relates to a method for purifying marine collagen, especially for enhancing the smell and appearance of marine collagen.
The invention further relates to a method for the production of porous sponges of marine collagen which are suitable in particular for medical purposes.
Collagen is a biodegradable as well as biocompatible protein which is used as a starting material for manifold applications in the food industry, in the pharmaceutical and cosmetic industries as well as in medicine.
“Marine collagen” is understood to mean collagen isolated from marine organisms, that is, organisms living in the sea, especially from members of the Porifera strain, preferably from Chondrosia reniformis. 
A large number of collagen products are known and being utilized in medicine. Such products include, for example, sponges, fibers or membranes.
The vast majority of these products is manufactured from collagen which is produced from the connective tissue, the skin, the bones, or the tendons of mammals, for example from cattle, horses or pigs. The essential disadvantages of these products are to be seen in the facts that:
in most cases, a young animal has to be used as the source for the collagen in order to obtain a sufficient yield of collagen;
the collagen obtained is in most cases soluble both in acid media as well as in basic media, which necessitates an additional crosslinking reaction (physically, by heat treatment, or chemically, by using bifunctional substances) in order to enhance the mechanical properties of the collagen and its stability in liquid media;
there is a risk of contamination with bovine spongiform encephalopathy (BSE).
As an alternative to producing collagen from mammals, International patent application publication WO 01/64046 describes a method for isolating collagen from marine sponges of the genus Chondrosia reniformis (Porifera, Demospongiae).
In this method, fresh sponge starting material is imbibed in alcohol and then washed with water, and an extracting agent is added thereto, preferably at a pH of 7-12. The resultant collagen extract is processed by increasing the pH of the suspension to a value of 8-11, stirring, centrifuging, subsequently lowering the pH value of the supernatant, as well as centrifuging and isolating the precipitate.
The sponge collagen obtainable by this method does, however, have disadvantages consisting essentially in that:
the collagen solution has a dirty appearance;
the collagen is microbiologically impure; and
products from this sponge collagen have an unpleasant smell.